The proposed research is a continuation of studies designed to evaluate the relative roles of the cell-mediated and humoral arms of the immune system in experimental candidiasis. Unmodified (normal) mice and mice immunosuppressed following adult thymectomy or treatment with cyclophosphamide (CY) will be studied from various perspectives. First, the development of cell-mediated immunity in such animals will be studied in vivo by footpad testing and in vitro by assays for lymphocyte transformation and migration inhibition factor. Three extracts of Candida will be studied in the in vitro assays, but one extract, designated ppt-HEX, will be studied in more detail both in vivo and in vitro. Secondly, since normal mice develop resistance to reinfection following cutaneous infection, attempts will be made to passively transfer such resistance to naive normal and immunosuppressed mice with cells or serum from normal immune mice. If cells transfer the resistance, attempts will be made to abrogate the transfer to preincubation with anti-0 serum. Thirdly, cutaneous lesions developing in normal and immunosuppressed mice in response to one or two inoculations of viable Candida albicans yeasts will be analyzed at selected intervals following inoculation for the number of colony forming units, and by immunoflourescence techniques for the infiltration of T and B lymphocytes into tissue surrounding the lesions. Finally, if time permits, additional studies are planned to assay for cell-mediated immunity in animals infected intravenously, to investigate the specificity of ppt-HEX, and to attempt to induce resistance to reinfection by artificial immunization with subcellular fractions of Candida.